In the operation of steam flooding to stimulate production of oil from oil reservoirs it is important to have a simple and accurate method to determine the quality of steam at the well head of an injection well. In such a stimulation process the amount of heat input to the reservoir determines the rate and amount of oil recovery, and heat input depends directly upon the steam quality. Steam that is generated for injection into the reservoir arrives at the well head as saturated or wet steam, i.e., a mixture of vapor and liquid, at super-atmospheric pressure. The greater the proportion of vapor in that mixture, i.e., the greater the steam quality, the more the heat input to the reservoir. Steam quality thus directly affects the rate and the ultimate amount of recovery of oil, and therefore has a bearing upon earnings and investment requirements.
One conventional method of measuring steam quality is by collecting a sample of the liquid phase of the steam and comparing the salt concentration of the sample with that of the feedwater to the boiler. However this method cannot be used if steam is distributed by a manifold system. Another method is by using an orifice plate and relating the pressure drop to the quality by use of a correlation. This method is accurate only in certain pressure ranges and again cannot be used in a manifold system.